The present invention relates to an exhaust gas recirculation system for an internal combustion engine of a vehicle, and more particularly to an exhaust gas recirculation system in which a recirculation pipe is provided to recirculate therethrough exhaust gases from an exhaust pipe into an induction pipe.
In such an exhaust gas recirculation system, it has been proposed that to reduce the nitrogen oxide content of exhaust emissions from the vehicle, flow control means may be adapted to control the flow quantity of exhaust gases through the recirculation pipe in accordance with changes of negative pressure from the induction pipe in relation to exhaust pressure appearing in the recirculation pipe upstream of the flow control means. However, with such a system, it is observed that reduction of the nitrogen oxide content of exhaust emissions inevitably disturbs good driveability of the vehicle and causes unnecessary fuel consumption.
It is, therefore, required that the flow quantity of exhaust gases through the recirculation pipe is precisely controlled in accordance with various changes of operative conditions of the engine to continuously ensure good driveability and proper fuel consumption.